fix(client): address PR #13 review — LOS tests, reset consistency, docs

- Use reset_test_state() consistently in test_snapshot_parsing.gd (Tyre critical)
- Fix misleading wall comment: (12,9) → (12,10) (Hoshe warning)
- Add coordinate space documentation to _test_snapshot() (Tyre warning)
- Add 4 Bresenham LOS unit tests: clear, blocked, diagonal, self (Hoshe warning)
- Check OS.is_process_running() in connection loop (Hoshe warning)
- Verify NPC position in corner reveal test (Hoshe suggestion)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/tests/test_sprint2_proof.gd

@@ -91,6 +91,9 @@ func _connect_to_server() -> bool:
 	_bridge = LocalBridge.new()
 	var elapsed := 0.0
 	while elapsed < CONNECT_TIMEOUT:
+		if _server_pid > 0 and not OS.is_process_running(_server_pid):
+			push_warning("Server process died during connection")
+			return false
 		if _bridge.get_status() == StreamPeerTCP.STATUS_NONE:
 			_bridge.connect_to_server("127.0.0.1", _test_port)
 		_bridge.poll()
@@ -174,6 +177,8 @@ func test_proof_corner_reveal() -> void:
 	var npc_found := false
 	for entity in snapshot.entities:
 		if entity.kind.variant == "Npc":
+			assert_float(entity.x).is_equal_approx(16.5, 0.001)
+			assert_float(entity.y).is_equal_approx(13.5, 0.001)
 			npc_found = true
 			break
 	assert_that(npc_found).is_true()